Idea for osciloscope with PIC

pic grafhics l.c.d scope

I have an idea for designing an oscilloscope with a PIC, I've never designed a project with external RAM memory on a PIC or used a ADC so I would apreciate any comments to know if is worth to research all the data for building this project.

PLease refer to the attached gif graphic:

The PIC controls the ADC and the RAM, when the sampling starts the pic waits for a sample to be ready, then commands the memory to store the sampled data, this process then repeats until the memory is full.

Once the memory is full the program running on the PC sends a signal to the DATA READY line to tell the PIC to start sending the data to the PC, the PIC controls the flow of data to the PC until all memory of the RAM has been transferred to the PC.

The program running on the PC shows the graphic.

The timing circuit controls the frequency of the ADC conversion.


Sorry about the very basic diagram, I have a much more detailed drawing but is not in electronic media so I just did a quick schematic.

The advantage I see in this design is that the ADC can be run at maximun speed as the data don't need to be transfered to te PC until the RAM is full, and also that the PIC don't need to be connected to the DATA BUS. Also you dont need to be near the PC when sampling the signal, you can sample and then download the data to the PC later.

Any comments are apreciated.

pic scope

You can strat form searching "Digital oscilloscope project" in this forum.

There you will find plenty of links and suggestions ..

osciloscope pic

Thanks IanP, I already checked those links and ideas but I have in mind a much more simple design. I just want to know if I'm on the right track or if there is some thing wrong with the way I'm planning to develope this project.

pic graphics lcd scope

Should your design include a PICmicro? Because I have some suggestion which is to use an external binary counter for address incrementing.The input clock to this binary counter comes from the ADC's end of conversion interrupt (ie. you won't need a timing circuit) with the ADC set to continous conversion mode...So all you do is just send a pulse to the ADC to start the continous conversion and the RAM will be automatically loaded with all samples in max speed.Then in second step of the program you will send clocks "manually" to the binary clock from the parallel port and read the samples from the RAM's databus... I haven't tried this idea but I hope it's useful

pic osciloscope

Hi mfacen,

It looks like it is possible. I would change it a bit. I would use the internal ADC and an External memroy ( you can use the internal flash of the PIC if you know how to read and write to the flash itself, and not the EEPROM ).
You will have to use an external ADC if we are talking about ADC that canot do what the PIC ADC can do.
Good luck with this.

osciloscope

Hi !

Mfacen, check for issue October 2000 of EPE magazine. There is a project very similar to yours. It is called Dual Channel Virtual Scope, using PIC 16F877 and a static RAM 6264. It stores the samples in the RAM and transfers to a PC where a software plots the signal. There are other similar projects you can find in the EPEs: April 2000 - Micropicscope (rudimentar scope using simple 16x2 LCD) and a May 2001 - PIC Graphics LCD scope.

Currently i´m building an old project called Easyscope from the extinct Popular Electronics magazine (nov/96). Originally it uses an obsolet PIC 16C71 that I replaced by a new 16F819. This is a very simple scope with no memory to store samples. All data is transferred via parallel port to a PC which has the control software.

Notice that all these projects have a very narrow bandwidth (no more than 40ksamples/s) which is adequate only to audio signals. This restriction is due to the very slow ADC from PICmicros. The dsPIC microcontrollers from MIcrochip have a much better conversion speed, aounf 500ksamples/s. Maybe an alternative to study.

good luck !

scope with pic

Thanks to all for the usefull ideas.

I'm using a external ADC because that way I can have a higher sample rate, the limit would be the speed of the ADC itself and of the write time for the RAM memory.

Te timing circuit I think is nesesary to set the sample rate as not allways I want to sample at te max rate.

I think is also very interesing the proposal from Always_Confused_Sudent to not even include a PIC in the project and replace it by a counter, I'll investigate that option too.

I checked EPE site some time ago but in the website they just offer back issues from 2001 in CD rom format. My problem allways is that I live in a small town in southern mexico and is really dificult to get literature down here. Rkdaira: do you have a copy of that magazine (EPE-october 2000) ? Is possible for you to post a copy of that article ?

I have seen on the web also a very simple osciloscope at http://www.geocities.com/lptscope/hw.html , great idea. Thats what I'm aiming for: the simplest ( and cheapest ) hardware, the problem I see with that design is the lack of reliability in Windows for timing. That's way I want to store the data in RAM and then transfer to PC at a lower rate.

The reason I'm designing this is because since I started with electronics I wanted a scope but with the economic situation down here is really difficult to buy one. I've seen in e-bay the sell used scopes really cheap, I tryied to buy a couple but the shipping costs where to high, about 180 Usd. I think a project like this would help lots of people in my situation. This project I'll try to keep under the 30 Usd for all the components.

picscope

mfacen said:

I'm using a external ADC because that way I can have a higher sample rate, the limit would be the speed of the ADC itself and of the write time for the RAM memory.

Click to expand...

Take a look at the bitscope deisgn.. The design originally won a Circuit Cellar competition.

Even though this may be a bit more highly spec'ed, there is a very good description of how things work. Also to get ideas for circuits to precondition your signal etc.

Hope this helps.

pic grafhics lcd scope

Hi,

If any one is interasted, i have a scope that is runing of the sound card. As you know, the sound card is and ADC an can sample signels quite fast...
The program is working great, all you need is to build/buy good probes.
Post your request and i will load it.

osciloscop cu pic

mfacen said:

I tryied to buy a couple but the shipping costs where to high, about 180 Usd. I think a project like this would help lots of people in my situation. This project I'll try to keep under the 30 Usd for all the components.

Click to expand...

There is a good project in polish magazine Elektronika Praktyczna EP-09/2003
they have it as a kit form " AVT 527+" the price for it is equivalent of 60 Usd incuding VAT.
(When selling abroad you do not have to pay VAT but the trasnsport cost is higher)

pic grafhics l.c.d scops

Mfacen,

Unfortunately I have only the printed paper issue of EPE and my scanner is not working, so I can´t provide you with the project. Sometime ago it was available at Edaboard downloads section. Bad luck !! If I could digitize the pages I will let you know. The source code and the PC software is available for download at:

**broken link removed**

Year 2001: PIC Graphics LCD Scope

pic graphic l.c.d.scope

Hello my brother!

I found these project surfing at my lunch time! I think better for Your purpose!

**broken link removed**


Gorkin.

pic grafics l.c.d scope

Thanks to everyone that responded to this post. I ordered the parts today and I'm going to be doing some soldering early next week. I still have some doubts about the input stage, conditioning the signal before the ADC, I'm aiming to just one input channel for now, I figure that once one is working is going to be easy to have maybe two chanels with external trigger and diferent input sensitivity.
I make PCB's the caveman's way. Just drawing the traces with a pen, that's why I have to keep this design simple, no transfer sheets arround here.
Is a while I'm wondering if the method of ironing a photocopy of a PCB and then etching really works ok. Some tips on how to do it maybe ? Thats the weak point of all my projects... No tracks going between IC's legs for me.

This is the best electronics forum I've seen so far. Keep it up !

circuit cellar bitscope

Hi gorkin,

Its a very nice site, its a pitty its not in english. I realy like the program for the LCD, but then again, its not in english and i couldnt realy paly with it.

diy logic scope lcd pic

Yes,the toner transfer method works fine...it's better with a laser print of the layout on a magazine gloss page...here are some tips...

**broken link removed**

pic graphics l.c.d scope

I'm trying to decide which RAM to use, I'm looking for some common IC available and cheap. Any sugestions ?

nokia lcd pic interfearence

Hi,


Take a look in this site :

h**p://kudelsko.free.fr/oscilloscope/sommaire.htm
With pic, serial, usb and more..........

how to build an osciloscopy

hi
this is the epe scan for picscope its in djvu format
goodluck
sarco

osciloscop cu pic si lcd nokia

Well I'm having a lot of problems with the input stage.

Funny: I need and oscilloscope to design this oscilloscope. What comes first: the egg or the chicken ?

pic osciloscop with lcd

have you seen the bitscopes 100MHz opensource oscilloscope.
if no go to this url:
www.bitscope.com
you can find the complete schematic ,full explanation and the sourcecode for it's PIC there.(except its CPLD's source)

( please one tell me how can i open the above picscope1_226.djvu file.)